The research hypothesis is that a mechanical property of the upper airway, specifically the elasticity (compliance) of the pharyngeal passage, is responsible for the initiation of upper airway obstruction during sleep. The objectives are a) to determine basic patterns of upper airway and chest wall muscle action which regulates upper airway patency, b) to measure the effects of passive (non-muscular) and dynamic (muscular) factors on upper airway size and compliance, and c) to assess the usefulness of tests of muscle activity and mechanical function in predicting the site of upper airway obstruction during sleep. Methods to be used include standard measurements, such as EMG activity and flow-volume loops, and new tools, such as NMR and acoustic pulse imaging in determining the function of the upper airway under static and dynamic conditions. Studies will be performed during wakefulness and, when appropriate, during sleep. Results from studies on patients and their families will be compared to findings in healthy subjects to identify traits responsible for upper airway obstruction during sleep. Population studies will assess the results from these physiologic studies. The career development goals are to continue extensive involvement in current research awards and to extend my education into new fields (genetic epidemiology, mucosal secretion, and airway microvasculature) relevant to future research. The RCDA award will provide and not merely replace salary support for the remaining years of the proposed studies and for one other, newly funded project, as well as provide support for time to learn and apply new techniques. Thus, this award will facilitate and promote my career toward the long-term goal of leading an academic section in pulmonary medicine.